Effective management of obstructive pulmonary diseases, especially Cystic Fibrosis (CF), represents a significant unmet medical need. Such diseases are characterized by thickened mucus that contributes to impaired lung function. This mucus barrier is composed primarily of cross-linked chains of proteins (mucins) complexed with nucleic acids released as a consequence of persistent lung inflammation and infection. In the case of CF, an autosomal recessive disease affecting approximately 30,000 patients in the US and 70,000 world-wide, current therapies designed to increase the fluidity of mucus and facilitate clearance involve the use of hypertonic saline inhalation to thin secretions and DNase enzymes (dornase alfa, trademarked as Pulmozyme) to digest mucus nucleic acids. In addition, half of patients with CF take four different medications, while about a quarter take upwards of six drugs including short-acting beta agonists, mucolytics, antibiotics, and inhaled and intranasal corticosteroids. There is consequently a great need to reduce treatment burden by developing formulations and delivery regimes that are compatible with existing therapies and delivery devices and that are effective across a broader percentage of CF patients. OrPro Therapeutics, Inc. is developing thioredoxins, a new class of mucolytic protein drugs with high efficacy and safety which specifically disrupt the thiol linkages between crosslinked mucin proteins. Reduced recombinant human thioredoxin-1 (rhTrx) has been demonstrated to be a highly potent liquefier of human CF sputum in laboratory studies. Trx is a small, stable non-glycosylated redox protein suitable for manufacturing in a range of prokaryotic and eukaryotic expression hosts and does not require mammalian cell expression. Our overall goal is to establish a formulation strategy for rhTrx that will support development of this molecule as a new and more efficacious mucolytic therapy for cystic fibrosis. A key component of such a therapy is a drug formulation that accomplishes the objectives of maintaining the protein in a stable, chemically reduced state (essential for its mucolytic and anti-protease functions) as well as facilitating compatibility wit modern, highly efficient aerosol delivery systems that minimize the treatment burden on CF patients. For this Phase I application, we plan to focus on laboratory-scale production of purified proteins (both native rhTrx control and a single amino-acid mutant variant, r(Cys)hTrx, having the potential to enhance safety and efficacy), physical characterization of these proteins in order to assess their chemical properties and relative activities, and initial preformulation studies to evaluate the suitability of thioredoxin for delivery via a range of nebulization devices. If the Ais of this project are achieved, key validation of the concept of disulfide reduction for mucolytic drug development will be established, enabling a Phase II project with the goal of focused development of specific formulations that will support preclinical studies leading to human trials of potentially safer and more efficacious treatment regimens that utilize improved, patient-friendly delivery devices. PUBLIC HEALTH RELEVANCE: There remains a critical unmet need for safe and effective treatment for Cystic Fibrosis (CF), the most common inherited lethal disease in Caucasian populations affecting more than 30,000 individuals in the United States. Our overall goal is to develop a new and improved mucus-disrupting (mucolytic) therapy for CF that is highly efficacious and which does not impose excessive treatment burdens on CF patients. We will accomplish this through development of optimal formulations of inhaled human thioredoxin, a recombinant protein mucolytic with a novel mechanism of action that has the potential to benefit a broader range of CF patients than current therapies.